Sync, Async, Blocking, Non-Blocking, Streaming are the buzzwords in the reactive programming world. This talk will attempt to attach some meaning to them. It will also demo the performance and resource consumption patterns for blocking-io, Scala Futures and RxJava Observables for comparable programs. Finally, a command line application that consumes twitter streams API will demo what is possible using the new reactive abstractions.

1. Demo the reactive jargons
Mushtaq Ahmed
ThoughtWorks
@mushtaqA

2. getProductPage
getModule1
getModule2
getPricing
getProductSpec

3. square(a: Int): Intsquares(a: Seq[Int]): Seq[Int]

4. Demo

5. ● Async and NonBlocking mean different things
○ Async is about API
○ NonBlocking is about Implementation
● Async API can be implemented for Blocking calls!
● For NonBlocking calls, Sync API is not possible!
○ Macros and CPS transformations can be used to fake it

6. Blocking Non-blocking
Sync square(a: Int): Int XXX
Async square(a: Int): Future[Int] square(a: Int): Future[Int]
API
Implementation

7. Demo

8. ● Blocking IO is contagious
○ ExecutionContext helps to quarantine it
● Separate ExecutionContext for Blocking and
NonBlocking IO
○ Like different speed lanes

9. Demo

10. ● Error handling in Future is a bit difficult for bulk
operation
● Observable is a nicer alternative
○ Yet to explore: Retry, Timeout etc
● Observable API does not support backpressure
○ Be Careful not to introduce memory leaks

11. Single Multiple
Sync square(a: Int): Int squares(a: Seq[Int]): Seq[Int]
Async square(a: Int): Future[Int]
squares(a: Seq[Int]): Future[Seq
[Int]]
squares(a: Seq[Int]): Observable[Int]
Observable[Int] == Future[Iterable[Future[Int]]]

12. The code for demo is here:
https://github.com/mushtaq/pune-scala-symposium

13. ● We like to teach Scala
● We are planning to offer a FREE training in Pune!
○ Screening based on coding test ;)
● 4 full day sessions
○ Two consecutive Friday-Saturdays
● Sometime in May or June
○ Will announce it via @punescala/Pune Scala meetup group

14. Thank you